Liquid reservoir for nebulizer

ABSTRACT

A liquid reservoir for a nebulizer is comprised of a pair of membranes formed of resilient material and sealed about their edges to form a closed chamber between them for containing a liquid to be nebulized. When the chamber is filled with liquid and thereby expanded, the resilient membranes are distended to apply pressure to the liquid in the chamber. A discharge valve controls the discharge of liquid from the reservoir to the nebulizer under the pressure applied by the membranes. The reservoir is mounted on the nebulizer so that one of the membranes abuts a surface of the nebulizer that concavely deforms the membrane to increase the pressure applied to the liquid in the chamber to reduce or eliminate any residual volume of liquid in the chamber at the end of the discharging operation.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to nebulizers and more particularlyto an improved reservoir arrangement for containing a liquid to benebulized.

[0002] Nebulizers, or atomizers, are devices that generate a fine sprayor aerosol. A particularly useful application for nebulizers is toconvert aqueous drug solutions, or suspensions with non-dissolvedparticles, into an aerosol of small droplets that can thereafter beinhaled to administer the drug to a subject during breathing. Suchinhalation treatment is highly effective for conditions effecting thesubject's respiratory organs. Further, since the lungs are close to theheart and the blood circulatory system of the body, drug administrationby inhalation provides an effective and rapid delivery system to allorgans of the body.

[0003] In many cases, the subject breathes with the aid of a respiratoryventilator. A typical ventilator has a breathing circuit comprising aninhalation limb and an exhalation limb connected to two arms of aY-connector. The third arm of the Y-connector is connected via a patientlimb to a mouth piece, mask, or endotracheal tube for the subject. Theventilator provides a desired degree of assistance to the breathing ofthe subject during the inhalation phase of the respiratory cycle. Thecontraction of the subject's lungs discharges gas through the exhalationlimb during exhalation. To achieve the maximum physiological effect forthe subject and to avoid wastage of the drug, the nebulizing action ofthe nebulizer is synchronized with the inspiratory phase of therespiratory cycle. A typical example of a nebulizer arrangement is shownin U.S. patent application Ser. Nos. 09/397,529, filed Sep. 16, 1999;09/547,523, filed Apr. 12, 2000; and 09/699,049, filed Oct. 30, 2000 andEuropean Patent Applications 311,773.6, filed Dec. 29, 2000 and311,778.5, filed Dec. 29, 2000 which applications are incorporatedherein by reference to the extent permitted. In nebulizers of the typeshown in the foregoing U.S. and European patent applications, the liquidis converted to an aerosol by the action of a vibrating element, such asa piezoelectric element. The supply of liquid from a liquid reservoir tothe nebulizing element is controlled by a valve. The liquid reservoir ispressurized to cause the liquid to flow through the valve to the elementwhen the valve is open.

[0004] In order to ensure maximum penetration depth of a nebulized druginto the lungs of the subject, the gas volume in the breathing circuitbetween the nebulizer and the lung should be minimized. To this end, thenebulizer is typically positioned near the patient mouth piece, mask, orendotracheal tube, i.e., in the patient limb of the breathing circuitdescribed above. However, for surgical and intensive care patients, thearea around the nose, mouth, neck and upper chest is often critical tothe care of the patient and/or crowded with other equipment. The overallsize of the nebulizer, including its liquid reservoir, thus becomes veryimportant. A liquid container remote from the nebulizer may be used toreduce the size of the nebulizer. However, if a small volume of drug isto be delivered, such an arrangement can be disadvantageous because ofthe amount of drug required to fill the liquid supply line between thecontainer and the nebulizer and the residuum of drug left in the supplyline. A local liquid reservoir mounted on the nebulizer would thus beadvantageous in such circumstances.

[0005] Such a local liquid reservoir for a nebulizer typically comprisestwo compartments separated by a moving wall. One compartment containsthe liquid drug. The other compartment contains a pressurizing gas. Themoving wall ensures that the drug is not contaminated by the gas. Theliquid compartment is filled with the drug by a syringe through afilling port. A syringe may also be used to pressurize the gascompartment. The reservoir so filled is mounted on the nebulizer tosupply liquid to the vibrating element of the nebulizer..

[0006] However, in such a local liquid reservoir, the gas compartmentadds to the overall size of the reservoir. As noted above, size is aserious concern for certain uses of the nebulizer. Also, pressurizationof the gas compartment is an additional maneuver required when using anebulizer of this type.

[0007] Another requirement for a local reservoir for a nebulizer is thatit be able to generate the necessary pressure to deliver liquid from theliquid compartment to the nebulizing element, including cases in whichthe inhalation limb and patient limb are pressurized by the ventilatorto provide breathing gases to the subject. It is also desirable that theliquid reservoir be capable of supplying the liquid independently of theposition or orientation of the nebulizer. To ensure that a proper drugdosage is administered to the subject and to avoid wastage of drug, itis desirable that the reservoir be capable of being completely emptied.It should be easy to fill the reservoir. At the end of the drugadministration, the reservoir should be easy to clean or dispose of.And, as noted above, the reservoir should be as small as possible,commensurate with the volume of liquid to be delivered to the subject.

BRIEF SUMMARY OF THE INVENTION

[0008] It is the object of the present invention to provide an improvedlocal liquid reservoir means for a nebulizer that advantageously meetsthe foregoing and other requirements.

[0009] Briefly, the present invention contemplates such a liquidreservoir comprised of a pair of membranes formed of a resilientmaterial. The membranes are positioned in an opposing relationship andsealed about their edges to form a closed chamber between them forcontaining the liquid to be nebulized. The chamber may be filled by asyringe or other appropriate means. Or, the chamber may be filleddirectly from a container through a check valve using a handle or othermeans, to draw the membranes apart in which case, the use of a syringemay be eliminated. When the chamber is filled with liquid and therebyexpanded, the expansion of the chamber distends the resilient materialmembranes to apply pressure to liquid in the chamber. A flow controlmeans, such as a valve, communicates with the chamber and controls thedischarge of liquid from the reservoir to the nebulizer under thepressure applied to the liquid by the distended membranes.

[0010] The liquid reservoir is mounted on the nebulizer so that one ofthe membranes abuts a surface of the nebulizer which concavely deformsthe membrane to increase the pressure applied to the liquid in thechamber. This pressure increase ensures that the liquid can bedischarged from the chamber against any pressures generated in abreathing circuit to which the nebulizer is connected. It furtherrenders the nebulizer insensitive to position as gases from thebreathing circuit cannot enter and become trapped in the reservoir.Still further, it reduces or eliminates any residual volume of liquid inthe chamber at the end of treatment, thereby ensuring that a patientreceives the proper total dosage of a drug and avoiding wastage.

[0011] Inasmuch as the local liquid reservoir of the present inventiondoes not use a pressurizing gas, the overall size of the reservoir canbe advantageously reduced due to the absence of a gas chamber.

[0012] The invention will be further understood from the followingdetailed description, taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0013] In the drawing:

[0014]FIG. 1 is a general schematic view of ventilator apparatuscontaining a nebulizer with a liquid reservoir means according to thepresent invention;

[0015]FIG. 2 is a general exploded and schematic cross sectional view ofa nebulizer and liquid reservoir means of the present invention;

[0016]FIG. 3 shows one embodiment of the liquid reservoir of the presentinvention in the unfilled condition;

[0017]FIG. 4 is a view showing the reservoir of FIG. 3 in the filledcondition;

[0018]FIG. 5 shows another embodiment of the liquid reservoir of thepresent invention; and

[0019]FIG. 6 shows a modification of a filling means for the liquidreservoir.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Nebulizer apparatus 10 of the present invention is typically usedin conjunction with breathing circuit 12 and ventilator 14, as shown inFIG. 1. Nebulizer 10 atomizes liquid solutions or suspensions fordelivery to a subject, as for example as a drug treatment for a patient.Breathing circuit 12 includes inhalation limb 16 coupled to ventilator14. Exhalation limb 18 is also connected to ventilator 14. Inhalationlimb 16 and exhalation limb 18 are connected to two arms of Y-connector20. The third arm of Y-connector 20 is connected to one end of patientlimb 22. The other end of patient limb 22 is connected to a mouthpiece,face mask, or endotracheal tube (not shown) for the subject forsupplying respiratory gases to lungs 24 of a subject.

[0021] Ventilator 14 provides all or a portion of the respiratory gasesfor the subject by providing inhalation gases in inhalation limb 16. Theinhalation gases pass through Y-connector 20 and into patient limb 22for supply to the lungs 24 of the subject. On exhalation, therespiratory gases pass through patient limb 22, Y-connector 20, andexhalation limb 18 back to ventilator 14.

[0022] As shown in FIG. 1, nebulizer apparatus 10 is preferablypositioned in patient breathing circuit 12 as near the subject aspossible to ensure effective delivery of the atomized liquid to lungs 24of the subject and to minimize the deposition of the liquid on thebreathing circuit walls. To this end, nebulizer apparatus 10 may beinserted in the breathing circuit between Y-connector 20 and patientlimb 22 as shown in FIG. 1.

[0023] The construction of a nebulizer apparatus suitable for use withthe liquid reservoir of the present invention is shown generally in FIG.2. Nebulizer apparatus 10 includes adapter 30 for connecting thenebulizer apparatus in patient limb 22 of breathing circuit 12. Housing32 is mounted in adaptor 30 in a manner to permit the housing and otherportions of the nebulizer apparatus to be removed from the adaptor forcleaning, when changing drugs, or for other purposes. Housing 32contains opening 34 through which nebulized liquid may pass.

[0024] A vibrating element 36, such as a piezoelectric element, ismounted in housing 32. The central portion of the vibrating elementcomprises a mesh plate 38 containing a holes 40. Holes 40 may be formedin plate 38 by an electro forming process that produces hose having adiameter of preferably approximately 2-15 μm in diameter. Vibratingelement 36 may be energized by high frequency alternating voltageprovided in conductors 42.

[0025] Plug member 44 is placed in the cavity defined by housing 32.Plug member 44 has a central opening 46 through which liquid to benebulized may pass to mesh plate 38. Opening 46 may be surrounded byelectrode 48 to provide, in conjunction with vibrating element 36, acapacitive means for determining the amount of liquid provided to meshplate 38. Conductor 49 is connected to electrode 48 for this purpose.Plug member 44 also includes electromagnet 50 for operating a valve,hereinafter described. Electromagnet 50 may be energized throughconductors 52. Conductors 42, 49, and 52 are contained in cable 54connected to nebulizer control unit 56.

[0026] As shown in FIG. 2, the upper surface 58 of plug member 44 isconvexly curved when viewed from the exterior of the plug member.

[0027]FIG. 3 shows one embodiment of liquid reservoir 60 of the presentinvention. Reservoir 60 is comprised of a first membrane 62 and a secondmembrane 64. As shown in FIG. 3, the membranes are juxtapositioned in agenerally opposing relationship. The membranes, which are shown ascircular in form in FIG. 3, are joined at their periphery and to form aclosed chamber between the membranes. The peripheral edges of membranes62 and 64 are joined to frame 66 which serves to mount reservoir 60 onplug member 44 as shown in FIG. 2. Bayonet fittings or other suitablemeans may be provided to fasten the reservoir on plug member 44.Membranes 62, 64 are formed of a resilient material, such as rubber orplastic.

[0028] One of the membranes, for example, membrane 64 contains a meansfor discharging liquid from reservoir 60. As shown in FIG. 3, the meansmay comprise a valve 68 which includes a disc-like plate 70 mounted inmembrane 64. Liquid conveying tube 72 depends from plate 70. A stopper74 is placed in tube 72 to rest on valve seat 76 formed in the tube.Spring 78 abuts stopper 74 to bias the stopper onto valve seat 76. Ashereinafter noted, the pressure of the liquid in reservoir 60 may alsobe used to press stopper 74 against valve seat 76. Stopper 74 is formedof a ferromagnetic material.

[0029] Membrane 62 contains a means for filling a chamber formed betweenmembranes 62 and 64 with liquid. As shown in FIG. 3, the means maycomprise a tube or luer lock fitting 78 suitable for engaging the end ofa syringe. Check valve 80 is located in tube 78 to retain the liquid inthe chamber. Check valve 80 may be formed of a plastic sealing meansthat deforms to provide an opening through which liquid may enter thechamber formed between the membranes. Or, the filling means may have acap for closing the filling means.

[0030] In use, liquid reservoir 60 is filled with liquid as byconnecting a syringe to tube or luer lock 78 and injecting fluid throughcheck valve 80 between membranes 62 and 64. The injection of the fluiddistends resilient membranes 62 and 64, as shown in FIG. 4, for formchamber 82. This distention pressurizes the liquid in chamber 82. Thepressure in chamber 82 assists spring 78 in sealing stopper 74 on valveseat 76 to retain the liquid in chamber 82. FIG. 4 shows liquidreservoir 60 in the filled condition.

[0031] After filling, liquid reservoir 60 is placed on plug 44 to inserttube 72 through electromagnet 50 in plug 44. Membrane 64 comes intoabutment with convex surface 58. As liquid reservoir 60 is pressed onsurface 58, membrane 64, as well as membrane 62, is concavely deformed,as shown in FIG. 2. This further increases the pressure applied by themembranes to the liquid in chamber 82. Liquid reservoir 60 is secured tonebulizer 10 by a connection between frame 66 and plug member 44.

[0032] Electromagnet 50 is energized through conductors 52 to liftstopper 74 off valve seat 76 and allow liquid from chamber 82 to flow tomesh plate 38. Vibrating element 36 is energized through conductors 42to nebulize the liquid and expel same through holes 40 in mesh plate 38.The energization provided in conductors 42 and 52 of cable 20 fromnebulizer control unit 56 may be synchronized with the respiratory cycleof the subject so that the atomized liquid is carried into lungs 24 ofthe subject with the breathing gases inhaled during the inspiratoryphase of the respiratory cycle. A triggering signal may be provided fromventilator 14 to nebulizer control unit 56 in conductor 84 for thispurpose.

[0033] The pertinent portions of plug 44 and liquid reservoir 60 may beformed such that the pressure applied to the liquid in chamber 82 whenliquid reservoir 10 is fastened to plug member 44 is sufficient tosecure the removal of substantially all of the liquid from chamber 82,even against the elevated breathing circuit pressure that may be appliedto chamber 82 from patient limb 22 through valve 68. That is, thepressure applied to the liquid in chamber 82 by the membranes formingthe chamber can exceed the pressure in patient limb 22.

[0034] As liquid is discharged from chamber 82, membrane 62 willapproach membrane 64. The convex surface of plug member 44, and theresulting concave deformation of membrane 64, is formed such thatmembrane 62 progressively contacts membrane 64, commencing from adjacentframe 66 and extending toward the center of the membranes. This assuresthat no residual liquid is left in chamber 82. For this purpose, surface58 may be formed such that the radius of curvature increases from theedge toward the center.

[0035] The applied pressure also renders nebulizer 10 and liquidreservoir 60 insensitive to position since gas from the breathingcircuit will not pass through valve 68 and become trapped in liquidreservoir 60 even if the liquid reservoir is upside down from theorientation shown in FIGS. 2 through 4.

[0036]FIG. 5 shows a further embodiment of the liquid reservoir of thepresent invention. In liquid reservoir 60 a, a handle 90 is mounted onmembrane 62. The end of tube 72 a may be sharpened, and used topenetrate a drug supply container, such as an ampoule. Handle 90 is usedto separate, or pull apart, membranes 62 and 64 to create an underpressure between the membranes. This suctions the drug from the drugsupply container into the chamber through valve 68 that, in this casealso operates as a check valve. The need to use an intermediate device,such as a syringe, to fill chamber 82 is thus avoided although liquidreservoir 60 must be disconnected from nebulizer apparatus 10 to fillchamber 82. Handle 90 may be removable, if desired, to minimize the sizeof liquid reservoir 60 a..

[0037] While in the foregoing description, liquid reservoir 60 is placedon plug member 44 after filling, it can also be placed on plug member 44before filling, if desired. This could occur, for example, if it isnecessary to refill chamber 82 to provide an additional dose of a drugto a patient

[0038] Also, while the foregoing has described the filling means 78, 80as mounted in one of the membranes 62, 64, it may also be locatedelsewhere on liquid reservoir 60, if desired. For example, it could bemounted on frame 66 as shown in FIG. 6.

[0039] It is recognized that other equivalents, alternatives, andmodifications aside from those expressly stated, are possible and withinthe scope of the appended claims.

1. Liquid reservoir means for supplying liquid to a nebulizer foratomization, said liquid reservoir means comprising: a liquid reservoirformed of first and second membranes positioned in a generally opposingrelationship to form a closed chamber between the membranes forcontaining liquid, said first and second membranes being formed of aresilient material, said first and second membranes having opposingsurfaces which are contiguous when the chamber is empty and spaced whensaid chamber is filled with liquid and thereby expanded, the expansionof the chamber distending said resilient material membranes to causesaid resilient material membranes to apply pressure to liquid in thesaid chamber; flow control means in communication with the chamber forcontrolling the discharge of liquid from the reservoir to the nebulizerunder the pressure applied to the liquid by the distended resilientmaterial membranes; and a member in the nebulizer having a surface towhich one of said first and second membranes is applied, said surface ofsaid member being formed to deform at least one of said first and secondmembranes to further increase the pressure on the liquid in saidchamber.
 2. Liquid reservoir means according to claim 1 wherein saidsurface of said member is formed to cause said membranes toprogressively contact each other, commencing at a periphery of themembranes and extending toward a center of the membranes.
 3. Liquidreservoir means according to claim 2 wherein said surface is formed sothat a radius of curvature of said surface increases from a periphery ofsaid surface to a center of said surface.
 4. Liquid reservoir meansaccording to claim 1 wherein said surface is formed to concavely deformat least one of said first and second membranes when viewed from theexterior of the chamber.
 5. Liquid reservoir mans according to claim 1wherein said flow control means is mounted in one of said first andsecond membranes.
 6. Liquid reservoir means according to claim 5 whereinsaid surface concavely deforms said one of said first and secondmembranes.
 7. Liquid reservoir means according to claim 6 wherein saidsurface of the nebulizer receives said flow control means.
 8. Liquidreservoir means according to claim 1 further comprising means forretaining said liquid reservoir on the nebulizer.
 9. Liquid reservoirmeans according to claim 1 further including filling means in fluidcommunication with said chamber by which liquid may be supplied to saidchamber.
 10. Liquid reservoir means according to claim 9 wherein saidfilling means is mounted on a membrane.
 11. Liquid reservoir meansaccording to claim 9 wherein said filling means contains a valve. 12.Liquid reservoir means according to claim 9 wherein said filling meanscomprises means engagable with a syringe.
 13. Liquid reservoir meansaccording to claim 9 wherein said filling means is mounted on saidretaining means.
 14. Liquid reservoir means according to claim 9 whereinsaid filling means comprises means mounted on a membrane for drawing themembranes apart to create an underpressure in the chamber formed betweensaid membranes and means mounted on a membrane to admit liquid to saidchamber responsive to said underpressure.
 15. Liquid reservoir meansaccording to claim 14 wherein said means to admit liquid comprises saidflow control means.
 16. Liquid reservoir means according to claim 15wherein said flow control means comprises a valve.
 17. Liquid reservoirmeans of claim 16 wherein said valve has an inoperative state in whichsaid valve operates as a check valve to prevent discharge of liquid fromsaid chamber and an operative state for allowing the passage of liquidthrough the valve when said membranes are drawn apart
 18. Liquidreservoir means of claim 15 wherein said flow control means has an endformed to engage a container for the liquid.
 19. Liquid reservoir meansof claim 14 wherein said means for drawing said membranes apartcomprises a means engagable by a hand of a user to draw the membranesapart.
 20. Liquid reservoir means of claim 19 wherein said meansengageable by a hand of a user is removable.
 21. Liquid reservoir meansof claim 1 further defined as a liquid drug reservoir means.